Reduction in radiation exposure is possible in testicular seminoma surveillance

Magnetic resonance imaging (MRI) is non-inferior to computed tomography (CT) for the surveillance of stage 1 testicular seminoma. Over a 6-year period, a 3-scan schedule was non-inferior to a 7-scan schedule regardless of imaging modality in the phase 3 TRISST trial. 

Stage 1 testicular seminoma has an almost 100% survival rate. Current international guidelines for the management of this cancer recommend CT surveillance of the abdomen/retroperitoneum following orchiectomy, with no adjuvant chemotherapy. While avoidance of chemotherapy avoids the risks and side effects associated with it, there are still long-term adverse health effects resulting from repeated exposure to radiation via multiple CT scans.

Prof. Robert Huddart (Royal Marsden Hospital and Institute of Cancer Research, UK) presented the results of the TRISST trial (NCT00589537) [1]. This phase 3, multicentre, factorial, non-inferiority trial aimed to assess whether CT could be safely replaced with MRI and whether the frequency of imaging could be safely decreased in surveillance of men with stage 1 seminoma. Investigators randomised 669 men to 1 of 4 arms, 2 of which were monitored with CT, and 2 of which were monitored with MRI. Each imaging modality arm had 2 different frequency schedules: one scanned patients at 6, 12, 18, 24, 36, 48, and 60 months; the other scanned patients at 6, 18, and 36 months. Patients randomised to the 3-scan arms only remained there in the absence of disease progression. All patients were followed for 6 years.

The primary outcome measure was the proportion of patients relapsing with Royal Marsden Hospital stage ≥2C disease. Of the 669 trial participants, 358 (54%) were deemed to be low-risk and 82 (12%) relapsed (see Figure). Only 10 of these 82 were graded as a stage ≥2C relapse. Most relapses were diagnosed at the time of scheduled imaging; additionally, relapse beyond 3 years was rare.

Figure: Relapse frequency for MRI versus CT and 3-scan versus 7-scan schedule [1]



Key secondary outcome measures included disease-free survival and overall survival rates; these were 87% and 99%, respectively. Values were similar across all groups. No tumour-related deaths occurred.

Although more events occurred in those who received 3 scans instead of 7, the criteria for non-inferiority were still met for both the intention-to-treat (ITT) and the per-protocol patients (upper 90% CI <5.7%). There were fewer events in those who received MRI scans than in those who received CT scans; 2 (0.6%) versus 8 (2.5%) (1.9% decrease; 90% CI -3.5% to -0.3% [ITT]). Per protocol results were similar.

Prof. Huddart asserted that surveillance is both safe and effective in stage 1 testicular seminoma, regardless of frequency or type of imaging. Furthermore, imaging beyond 3 years may be unnecessary, as relapse after 3 years is rare. Finally, they recommend that the standard of care should recommend MRI instead of CT, in an attempt to limit radiation exposure in this young population.

1. Joffe J. Imaging modality and frequency in surveillance of stage I seminoma testicular cancer: Results from a randomized, phase III, factorial trial (TRISST). Abstract 374, ASCO Genitourinary Cancers Symposium, 11–13 February 2021.

 

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Posted on 24 March 202118 June 2021